Description

A gentleman treated 6 years ago for colonic carcinoma (stage-IIA) had been on regular follow-up for a span of 4 years, when
he was apparently disease-free. After being lost to follow-up in the past 2 years, he was recently diagnosed with a pathological
fracture of the seventh thoracic vertebra (figure 1) for which he underwent surgery (vertebral fixation and cord decompression) on an emergency basis.

Postoperatively, he underwent a CT simulation of the thorax with the purpose of planning radiotherapy (RT) to the involved
vertebrae. The CT-scan demonstrated multiple bilateral pulmonary nodules (figure 2). After palliative RT to the involved vertebral column, in the interest of academics, we utilised the CT-scan data for volumetric
reconstructions to attempt a better depiction of the well-known phenomenon of ‘cannon ball metastases’.1,2 This was achieved by the use of Slicer 4.2, an open source software package (distributed under a BSD-style open source license)
intended for advanced visualisation and analysis of medical image datasets.3 This, to our knowledge, is possibly the first publication providing a three-dimensional depiction of ‘cannon ball’ pulmonary
metastases (figure 3).

Three-dimensional rendition generated out of the thoracic CT-scan data, demonstrating ‘cannon balls’ within the lungs.

Slicer 4.2 is free to download and is available for use with the Linux, Mac and the Windows operating systems.4 While the package already contains numerous features, additional functionality can be via the in-built ‘extension manager’,
which provides options to integrate various extra features. Though it is not currently approved for clinical use, it can,
however, be used freely for academic research.

Learning points

The importance of adherence to follow-up remains undiminished even after initial years of uneventful follow-up, regardless
of the stage of cancer.

Volumetric imaging data from sectional imaging can be digitally reconstructed to provide enhanced visualisation of normal
and pathological anatomy.

Slicer 4.2 can be downloaded freely from http://www.slicer.org/pages/License, and being a feature-rich open source alternative to expensive commercial software, it can handle complex functions such
as tractography, multivolume processing, etc.

Though not approved for clinical use, Slicer 4.2 can freely be utilised for research purposes.